The present invention relates to a portable gas pressure welding machine for gas pressure welding rails together and punching-shearing excess metal formed on the welded portion of the rails and, more particularly, to a small-sized gas pressure welding machine for rails with two separate mechanisms for punching-shearing excess metal, which machine comprises a combination of a pressure application unit mounted along rails to be welded together and provided with a mechanism for punching-shearing excess metal from the lower surface of the rail foot and an excess metal punching unit fitted on the railhead and provided with a mechanism for punching-shearing excess metal from the railhead, rail web and upper surface of the rail foot.
As for the related art, there are cited Japanese Patent Publication No. SHO 53-4060, U.S. Pat. No. 4,556,164 and U.S. Pat. No. 4,576,324, for example. The Japanese Patent Publication discloses a gas pressure welder comprising in combination a movable pressure application bed for clamping one of rails to be welded together through connecting media of a plurality of guide stays and applying pressure to the other rail, a stationary bed for clamping the other rail and receiving the pressure from the movable bed, and punching-shearing means, which are assembled together so as to be movable relative to one another. Therefore, the welder is generally large in size and heavy in weight. Furthermore, the welder has to be fitted on rails by raising the entire body thereof. Since the welder is heavy in weight, it is required to use a crane or the like in fitting the welder on rails. This means that the welder is inferior in maneuverability in the working of transportation, installation and field welding and that much labor is required.